Citation and License

Abstract

Background

Chemoprevention crossover trials of tea can be more efficient than parallel designs
but the attrition and compliance rates with such trials are unknown.

Methods

Attrition (dropouts) and compliance with treatment were assessed in a 25-week randomized,
placebo controlled, crossover, feasibility clinical trial of four tea treatments to
investigate the effect of tea on oral cancer biomarkers. Each treatment lasted 4 weeks
with 2 weeks of washout in between. Participants were 32 smokers and 33 non-smokers
without any evidence of premalignant oral lesions. The interventions consisted of
packets of green tea, black tea, caffeinated water, or placebo. Participants were
assigned to each treatment for four weeks, and were instructed to drink five packets
per day while on the treatment. Dropout from the trial and compliance (consumption
of ≥ 85% of the prescribed treatment packets) are the main outcome measures reported.

Results

There was a high rate of dropout (51%) from the study, and the rates were significantly
higher among smokers (64%) than non-smokers (36%). Among participants who completed
the study the rate of compliance was 72%. The highest rates of dropouts occurred between
the first and second treatment visits in both smokers (38% dropout) and non-smokers
(18% dropout). Throughout the study smokers were more likely to dropout than non-smokers.
Black tea treatment was associated with the highest rates of dropout among smokers
(37%), but was associated with the lowest rate of dropout among non-smokers (4%).

Conclusions

In a study conducted to test the feasibility of a four-treatment crossover tea trial,
a high rate of dropout among smokers and non-smokers was observed. Multi-arm crossover
tea trials might pose a higher burden on participants and research is needed to improve
adherence and treatment compliance in such trials.